It is well known that oil and gas wells have a finite lifetime and that the production rate of an individual well will decrease gradually until resource extraction no longer becomes profitable or until regulations mandate that production from the well must be suspended.
In most cases, as oil and gas wells mature, production volumes decrease as the bottom-hole pressure decreases. This results in produced fluids from the reservoir reaching a critical velocity that eventually does not permit the liquids to reach the surface without some form of artificial lift. When these liquids aren't completely removed from the well with the oil and gas production from the reservoir, they build up in the well, causing the oil and gas to flow intermittently, lowering production and eventually killing the well. This is phenomenon is known as “liquid-loading.” Liquid loading is particularly problematic for conventional artificial lift equipment when the liquids contain significant volumes of particulates such as fine mud, sand and silt.
PCT Publication No. WO2010/009496 describes a gas displacement pump for use in pumping liquids for recovery of oil from stripper wells.
U.S. Pat. No. 5,074,758 describes a pump for moving liquids or slurries which is particularly adapted to move dangerous and corrosive liquids.
U.S. Pat. No. 5,373,897 describes a pneumatic underground fluid recovery device for use in a well to pump underground fluids therefrom.
U.S. Pat. No. 6,027,314 describes a pneumatically powered submersible fluids pump with a casing activator.
There remains a need for a solution to address and improve the rate of production and ultimate reserve recovery from oil and gas wells loaded with sandy, silty, muddy liquids. In most cases the particulate material in wells producing these types of liquids in conjunction with oil and gas causes conventional rotating or reciprocating artificial equipment to fail prematurely. Currently, the problems caused by sand, mud and silt are addressed using siphon string technology.